As is well known in the art, the indoor coil in a vapor compression refrigeration system typically is required to be defrosted from time to time. Various devices and methods in this regard are known. The more commonly known defrosting methods, i.e., electric defrost and the off-cycle defrost, have certain disadvantages.
Reverse cycle defrost is a less commonly used defrost method, partially due to the limited ambient temperature range in which acceptable defrost performance is feasible. In certain conditions, there may be insufficient thermal energy in the refrigeration system for effective defrost of an indoor coil during operation in defrost mode. For instance, in the prior art, in situations where an outdoor coil of a refrigeration system is subjected to ambient conditions, significant changes in the ambient conditions may have an impact on the defrost performance of the refrigeration system. In particular, low-temperature ambient conditions may cause a number of problems in the operation of the refrigeration system. For example, when using known reverse cycle defrost methods in low-temperature ambient conditions, a relatively long time is required for defrosting. However, in practice, the length of time in which the system may be in defrost mode is limited.